The invention relates generally to automatic test equipment, and more particularly to a reduced-cost manipulator apparatus employed for use with automatic test equipment.
Automatic test equipment provides semiconductor device manufacturers the ability to test each and every device fabricated. By testing each device, the manufacturer can sort devices having like speeds, and/or separate failed devices from passing devices. In this manner, the manufacturer is able to confidently put fully functioning devices into the marketplace.
Automatic test equipment, often referred to as a tester, typically employs a mainframe or computer workstation and a testhead. The testhead houses sophisticated electronics and includes interface circuitry for coupling the electronics close to the devices-under-test (DUTs). This is done in order to minimize propagation delays on the test signals transmitted between the testhead and the DUTs. The DUTs are typically positioned on a prober (if at the wafer level) or handler (if at the packaged-device level).
Due to the size and weight of a conventional testhead, coupling the tester electronics to the DUTs involves carefully docking the testhead to the handler or prober (hereafter generically referred to as a handling device). The device employed to carry and position the testhead for docking is a manipulator. FIG. 1 illustrates a conventional manipulator 10 adapted for carrying and positioning a testhead 12.
Further referring to FIG. 1, the conventional manipulator includes a base 14 and a cradle 15 for engaging and carrying the testhead 12. A positioning mechanism 16 provides the ability to displace the two-thousand pound testhead along a plurality of compliance axes with manual control. Conventionally, one example of the mechanism includes high-precision linear bearings 18 that cooperate with telescopically sliding members to provide compliance needed to carefully position the testhead. Generally, compliance refers to the force applied by the manipulator to offset the force of gravity acting on the testhead. Once leveraged out, the compliance allows the testhead to be moved around in any direction. The mechanism is actuated by a pneumatic or hydraulic piston 20. Alignment pins (not shown), help to guide the testhead onto the handling apparatus.
While this example of a conventional manipulator works well for its intended applications, the mechanical construction for establishing compliance employs parts and assemblies built to a high degree of precision with very tight tolerances. This translates into a high cost of fabrication.
What is needed and currently unavailable is a manipulator solution that provides multiple axes of compliance with low-cost components. The low-cost manipulator of the present invention satisfies this need.
The manipulator of the present invention employs low-cost components to effect reliable and accurate multi-axial compliance without sacrificing performance. This correspondingly reduces test costs for semiconductor device manufacturers.
To realize the foregoing advantages, the invention in one form comprises a compliance assembly for use in a semiconductor tester testhead stand. The compliance assembly includes an airspring having compliance along a plurality of axes and a containment vessel adapted for receiving the airspring. The containment vessel includes walls that, when the airspring is loaded, control the compliance along the plurality of axes.
In another form, the invention comprises a testhead stand for compliantly docking a semiconductor tester testhead to a handling apparatus. The testhead stand includes a base having oppositely disposed side members and a pair of spaced-apart extension members. The extension members are disposed on the side members and project upwardly therefrom. A pair of compliance assemblies disposed on the pair of extension members are adapted to receive the testhead. Each compliance assembly includes an airspring having compliance along a plurality of axes and a containment vessel. The containment vessel is adapted for receiving the airspring and has walls that, when the airspring is loaded, control the compliance along the plurality of axes.
In a further form, the invention comprises a linkage-based manipulator for automatic test equipment. The linkage-based manipulator includes a base and a cradle having a testhead end adapted for coupling to a testhead. The manipulator further includes a linkage means for vertically displacing the cradle between a lower position and an upper position while maintaining the cradle parallel to the base and while avoiding any horizontal displacement. A load element pivotally mounted at one end to the base and at the other end to the linkage means provides a force to the linkage means opposite the force of gravity acting on the testhead.
Other features and advantages of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.